Traditionally, mechanical equipment such as engines and machines incorporating a housing has been maintained by regular maintenance schedules. In the event of a malfunction, an operative or engineer will run the machine or engine through a series of test Functions in a trouble-shooting programme and take note of the reaction of the machine or engine to each test function from an observation of the action or reaction of the machine to a given test function, it is possible to diagnose at least in part, the general area of malfunction of the machine. Thereafter, the machine is dismantled to an extent sufficient to enable the possible malfunction to be identified and a repair effected.
Our co-pending British Patent Application No 00200461.0, the disclosure of which is incorporated herein by reference, describes and claims apparatus comprising a work head adapted to carry a tool or examination element for work or examination at a site internally of a machine, which apparatus comprises a support arm for a work head, said arm being adapted to enter within said machine to position the work head in the desired operating position, operating means for operational control of said work head and control means for controlling the attitude and positioning of the arm within said machine wherein the support arm comprises at least one segment having a plurality of links, each link being articulated with respect to its neighbour and means for controlling the position and/or attitude of said segment relative to a datum thereby enabling the arm to follow and adapt to a predetermined path within the machine from entry in the machine housing to the work site.
In a particular aspect of the invention described in that application, each segment comprises a plurality of links, there being a degree of articulation between adjacent links. By maintaining articulation of the links in each segment under tension, the spatial positioning of each segment can be controlled with precision to enable the arm to follow a convoluted path to guide the work tool into the machine. An arm of this type is sometimes referred to as a “snake”, “snakey” or serpentine arm because of its ability to extend axially of itself in the manner of a snake and to flow around obstacles in order to follow a convoluted path.
The invention described in British Patent Application No 0020461.0 requires precision engineering of each component to minimise frictional losses at the point of articulation between each pair of links. In a multi-link segment, these friction losses build up and in a multiple segment robotic arm; the overall friction losses to be overcome during manipulation of the arm can be considerable. There is a need, therefore, for a device in which the manufacture of the components is relatively straightforward and in which the friction losses can be reduced. In the device specifically described in British Patent Application No 0020461.0, spring means may be provided to bias each of the links against the compressive tension force being exerted by the control cables.
The present applicants have found that by dispensing with the springs and interposing instead a layer of rubber or elastomeric material either bonded or keyed to the two members constituting the articulation between adjacent links within a segment, the rubber can constitute a fixed frictional contact surface between the articulated components while at the same time providing the resilient shear capacity necessary to produce “stiffness” of the joint.